Automatic titration system



Feb. 3, 1953 R. T. SHEEN 2 3 AUTOMATIC TITRATION SYSTEM Original FiledMarch 17, 1 948 7 Sheets-Sheet 2 lNVENTOR Feb. 3, 1953 R, SHEEN2,627,453

AUTOMATIC TITRATIQN SYSTEM Original Filed March 17, 1948 7 Sheets-Sheet3 INVENTOR IMLZQ.

ATTORNEYS Feb. 3, 1953 R. T. SHEEN 2,627,453

AUTOMATIC TITRATION SYSTEM Original Filed March 17, 1948 7 Sheets-Sheet4 w M5 M9 M ma m5 INVENTOR Sheer :1 QQQW ATTORNEYS Feb. 3, 1953 R. 'r.SHEEN AUTOMATIC TITRATION SYSTEM Original Filed March 1'7, 1948 7Sheets-Sheet 5 INVENTOR RobafZS/wm TTORNEYS m 3 m R w s E L x v m 2 t amy. w 5 i mm 2 0 I a JV 7 I 6 4, 5

M E m m 2 a a 3 W mm l5 6 5 R 2 T .C 2 R 7 M a w W a A Feb. 3, 1953Original Filed March 17, 1948 Feb 3, 1953 R. T. SHEEN 2,627,453

AUTOMATIC TITRATION SYSTEM Original Filed March 17, 1948 7 Sheets-Sheet7 INVENTOR ATTORNEYS.

Patented Feb. 3, 1953 AUTOMATIC TITRATION SYSTEM Robert T. Sheen,Wyndmoor, Pa., assignor to Milton Roy Company, Chestnut Hill, Pa., acorporation of Pennsylvania Original. application March 17, 1948, SerialNo.

1949, Serial ND. 101,106

2 Claims.

The-present invention relates to chemical titrationsystems of thecharacter which may be employed to maintain a particular chemicalconcentration in a solution.

The present application is a division of my application Serial No.15,431, filed March 17, 1948, for Automatic Titration System.

My applications Serial No. 101,105 filed June 24, 1949 for TitrationSystem and Serial No. 173,650 filed July 13, 1950 for Titration Systemrelate to processes and apparatus for titration under constant endpoints.

The solution whose concentration is being controlled is herein calledthe main solution. The additive to the main solution is a concentratedform of the ingredient whose concentration is being controlled.

A purpose of the invention is to facilitate the control of chemicalconcentration in strong solutions in which the direct measurement ofconcentration is difficult.

A further purpose is to withdraw a fractional metered sample from themain solution, to titrate such sample by a samplereagent introduced inaccurate proportion to the sample, to an end point at which theconcentration can be measured accurately, and to control theintroduction of a main reagent into the main solution in accordance withthe concentration measured at the end point.

A further purpose is to pump off continuously a stream of fractionalsample from the main solution, to concurrently pump a stream of samplereagent, preferably by duplex pumps having a common drive, to titratethe sample by thesample' reagent, to' continuously sense theconcentration of the titration mixture at the end point, to pump themain reagent into the main solution and to control the feed of the mainreagent in accordance with the concentration of the titration mixturewhich is sensed.

A further purpose is to employ a duplex pump for the fractional sampleand for the sample reagent, both pump units of which are operating inphase.

A further purpose is to control a strong acid or strong alkaliconcentration in the main solution by pumping off continuously afractional metered sample, pumping into the fractional sampleaproportional metered quantity of alkali or acid sample reagent, as thecase may be, to attain an end point, to sense the hydrogen ionconcentration at the end point, and to control addition of acid. .oralkali to the main solution thereby.

Divided and this application June 24,

A further purpose is to pump off a fractional sample from the mainsolution and meter thesame, to dilute the sample by aproportionalmetered quantity of diluent, to sense the conscentration ofthe diluted sample and to control the addition of main reagentinaccordance with the concentration sensed.

A further purpose is to regulate the oxidation potential of a mainsolution by continuously pumping off a metered sample, continuouslypumping into the sample a proportional metered quantity of oxidationpotential sample reagent of a character opposed to that of the mainsolution, continuously sensing the oxidation potential of the mixture ofsample and sample reagent, introducing oxidation potential main reagent:to the main solution, and regulating the quantity of oxidation potentialmain reagent in accordance with the oxidation potential of the mixtureof the sample and sample reagent as: sensed;

A further purpose is to blanch vegetables, such as peas. by feeding thevegetables through a main solution containing a strong al aliconcentration, continuously pumping off a metered quantity of" the mainsolution as a fractional sample, con tinuouslv metering and titrating anacid reagent, preferably a buffer acid reagent, with the sample,continuou ly sensing the h drogen ion concentration of the titrationmixture, adding alkali main reagent to the main solution and controllingthe addition of al' ali main reagent in accordance with the hydrogen ionconcentration of the titration mixture.

A further purpose is to control the concentration of a strong acidsolution, of a strong alkali solution, for example for textile treating,or of a textile bleach solutionsuitably of chlorineor hydrogen peroxide.

Further purposes appear in the specification and in the claims;

In the drawings 1'- have chosen to illustrate a few only of the numerousembodiments in which my invention may appear, choosing the forms shownfrom the standpoints of convenience in illustration, satisfactoryoperation and clear demonstration of the principles involved.

Figure 1 is a diagrammatic illustration of a system of titrationembodying, the invention,

Figures 2 and 3 are curves useful in explaining the invention.

Figure 4 is a diagrammatic top plan view of a duplex pump which may beemployed in the invention.

Figure 5' is a top plan view of a micro-adjush ment for one of the pumpsor. pump units;

Figure 6 is a circuit diagram showing a motor and. its connections.

Figure 7 is a section of Figure on the line ll.

Figure 8 is a section of Figure 5 on the line 8-8.

Figure v9 is a section of Figure 8 on the line 99.

Figure 10 is a section of Figure 9 on the line l0|0.

Figure 11 is a diagrammatic illustration of a variation in the system oftitration in accordance with the invention.

Figure 12 is a diagrammatic top plan view of a variation in the duplexpump.

Figure 13 is a plan view of the preferred embodiment of titrationchamber.

Figure 14 is a side elevation of Figure 13.

In the prior art considerable difficulty has been encountered incontrolling the chemical concentrations of strong solutions due to thefact that control sensing elements are diificult to apply in suchsolutions, and are likely to be inaccurate. It has been proposed (Smith1,684,645) that the hydrogen ion concentration of a main solution bechanged by drawing oiT a sample through a constant orifice variable headdevice into a constant head device, supplying a reactant through aconstant orifice constant head device which will bring the concentrationinto a range which can be readily measured, and controlling the additionof a main reactant into the main solution in accordance with thetitration of the sample and the sample reactant. This device operateswith considerable inaccuracy and considerable time lag.

In accordance with the present invention it is possible to control astrong concentration in the main solution continuously with a highdegree of precision by continuously pumping off a sample from the mainsolution, continuously combining with this sample a sample reactantwhich is pumped in proportional quantity to the sample, and'controllingthe additions of main reactant to the main solution by sensing theconcentration of the titration mixture, that is, electricallydetermining the end point of titration as an electrical characteristic.The fractional sample and the sample reactant are most desirablywithdrawn by a duplex pump having a common drive, so that, once theproportion between the sample and the sample reactant is determined, thefeeds are for the time being constant, and the variation is in theconcentration of the titration mixture in accordance with the change inthe concentration of the sample. The two pumps preferably will operatein phase, so thatvariations in titration will not occur on account ofvariations in pumping. The volume of the titration chamber is selectedso that it will preferably exceed one minutes pumping capacity of theduplex pump, so that the equipment willnot hunt, and the increments ofchange will be small.

The process according to the invention has the advantage over thoseprocesses which titrate the main solution that the main solution is notloaded up with salts or other products of titration, and the choice ofthe titration reactant is not limited by the character of the process inwhich the main solution is used. Thus the sample reactant which performsthe titration may be a buffer when a buffer would be undesirable in themain solution, and may be a toxic substance when the main solution mustbe free from toxicity.

The present device is much more positive than the variable head variableorifice or fixed head variable orifice devices of the prior art.

The principles of the invention are applicable to concentrations ofvarious characters, such as acidimetry (and of course alkalimetry),control based on ion content such as conductivity, control based onoxidation potential, or'the like. The character of the sample reactantand the main reactant will depend on what concentration is beingcontrolled, for example in the case of acidimetry the sample reactantmay be an acidimetry reactant of the proper concentration, or a diluent,while in the case of oxidation potential characteristics the samplereactant will be a reducing agent if the main solution is oxidizing, andan oxidizing agent if the main solution is reducing.

Likewise a color reactant may be employed, sensed by a photometer orcolorimeter.

Referring to Figure 1, a container 20 is shown for the main solution,which may have any suitable shape, whether that of a treating vessel asindicated, or that of a conduit or pipe. If desired to add makeup waterindependently so as to hold volume, or level, this can be accomplishedthrough a pipe 2| through float control 22 (suitably including a floatin the tank, not shown) from a source 23.

A main reagent 24 in a container 25 is introduced to the main solution26 through a pipe 2'! under metering control later to be described. Themain solution will commonly be used for process treatment, as indicatedby a dotted line 23 suggesting flow of material through the mainsolution, with accompanying change in composition of the main solutiondue to "drag out of main solution with the material processed, and dueto chemical reaction between the reactant and the material beingprocessed. It will be understood, however, that the main solution may beused for any other suitable purpose.

In order to accomplish the control of the additions of main reactant 24,a fractional sample of the main solution 26 is continuously withdrawnthrough a pipe 30 by a metering device, preferably a metering pump 3|,driven by a drive 32 and feeding to a titrating chamber 33. Thus acontinuous sample is obtained, which in quantity will suitably be aminute proportion of the total main solution, but in any case will berepresentative of or will bear an established relation to the mainsolution. While the metered feed from the pump 3| will preferably bemade adjustable as later explained, for any given indefinite period ofoperation, the sample will be withdrawn at a rate which is suitablyinvariable.

In order to titrate the sample, a sample reagent 34 in solution or otherliquid form from a container 35 is supplied by a pipe 36 through ametering device, suitably a metering pump 35', having discharge which isproportional to that of the metering device 3|, preferably by virtue ofthe fact that the two pump units are driven by the same drive 32, thusconstituting a single duplex pump. The cylinder volumes and/or strokesof the pistons are adjustable to provide the desired proportional feedof the sample reagent to the fractional sample, and for a suitablyindefinite period proportionally will remain the same and the end pointconcentration in the titrating chamber 33 will accordingly vary with theconcentration of the sample. The titrating reaction mixture willsuitably be discharged from the titrating chamber 33 as by an overflowpipe 31, the discharge being wasted or recovered as desired but normallynot returned to the main solution. The level of overflow or the overflowresistance at 3'! will be set to assure an adequate pressure"differential across pumps 31' and :35" to assure metering actionby thesepumps;

A feature which differs from usual titration is that the end pointconcentration in the titrating chamber is constantly varying. Inordinary titration with an indicator, the end point concentration isinvariable and the quantity of reagent added varies with the sampleconcentration, but with the present system the sample reactant additiondoes not change for an indefinite period.

A sensing element 38 of suitable character is in contact withthereaction mixture in the titratingcontainer, and will be of any wellknown type which responds to theparticular charac' teristic which isbeing controlled. For example if hydrogen ion concentration isbeingcontrolled, a hydrogen ion sensing element of any well known type, suchas a glass electrode, may be used. If total ion concentration is beingcontrolled, a conductivity sensing element of well known character willbe employed. If oxidation potential is being indicated, a sensingelement for oxidation potential of well known character may be used. Thesensing element may also sense by color, viscosityor specific gravity aswell known. Correspondingly if the concentration of any particular ionis be'ing'controlled, a sensing element responding to the concentrationof that ion will be employed.

The sensing element is connected to an automatic indicator or preferablya recorder 46 of well known character, as it is usually desirable wiring44 controls the drive 45' of a metering" pump 46 in the main reagentpipe 21, so that the quantity of main reagent supplied to the mainsolution is controlled by the concentration indicated by the sensingelement.

As best seen in Figure 2,. a typical titration curve 41 is shown, usingas ordinates the voltage across the sensing element and as abscissae theconcentration oftheparticular reactant present inthe main solution- It.will be noted that over a particular concentration. range abcorresponding. to one extreme concentration. of the reacta-nt' andv overanother concentration range. 6! corresponding to an opposite extremeconcentration of the reactant, very little. difference 111 .:V01tageresults iromconsiderable change in concentration. For example, ifhydrogen ion concentration is being controlled, the portion ab of thecurve might correspond to the condition for a strong acid solution andthe portion e1 would therefore correspond to the condition for astrongly basic solution. Neither of these ,concentrations can beaccurately controlled by directly sensing the voltage across the sensingelement. By the addition of the sample reactant,- however, which is ofopposite chemical character from the-main reactant, the concentrationin. the sample will move into the range of the portion of the curve cdwhich corresponds to a much weaker solution than. that corresponding totheextremes. At the portion cd of thecurve a very considerable voltagechangeoccurs for a small change-inconcentration and. therefore highlyaccurate control can. be accomplished.

Where hydrogen ion concentration is being controlled, the samplereactant willv preferably be a: bufier acid or alkali in .suflicientconcentration --to bring the hydrogen ion concentration in thetitratingchamber into a range for accurate control. Thus if the main solutioncorresponded to the rangegh oncurve48 of Figure 3 (which. plots-pH asordinates against concentration of buffer acid as abscissae'), thesample reactant would bring the concentration into the rangec'y' or km"at which accurate control could'be acoom. plished.

Unbuffe'red' acids such as sulphuric, nitric,' hydrobromic, .orhydrochloric will preferably not'beused, w-here the main-solution isalso unbuffered, as a variation in addition of sample reactant wouldcausea-very wide-variation in thepHi A much more gradual slope of thecurve is desired, so that for any given addition of sample reactantwithin areasonable tolerance there will be only one-characteristic pH,thus accomplishing a very small change in pH for a given small incrementof buiier sample reactant. Suitable buffer acids which may be used assample reactants are phosphoric, acetic, oxalic, citric, tartaric,carbonic and boric acids. Suitable buffer alkalis are trisodiumphosphate, .sodium carbonate, sodium borate, and sodium metasilicate. Ingeneral the buffer acids and alkalisare less than 50% ionized, and inthe great ma'jorityof cases are not more than 10% ionized. ,In the eventthat the main solution issufiiciently buffered, a strong acid or alkalimay be usedas the sample reagent.

For example, using buffer acids and alkalis rather than the completelyionized type, it is possible to control the hydrogen. ion concentrationwithin plus or minus 0.004 normal rather than 0.02 normal, which wouldbe diflicult to obtain with the non-buffered sample reactant.

A very simple construction of the duplex pump is shown in Figure 4:, inwhich the individual pumps have their pistons 54 and 5! operating incylinders '52 and 53 and connected to cranks 5'4 and 55 on the drive 32by connecting rods 56 and 51.

The piston strokes are adjustable in any suitable way, as for example byadjusting the crank arms-by any suitable means, such as is shown.

It will be seen. from this View that instead of being 180 out. of phaseas in prior art duplex pumps, the pumps 3i and 35 operate in phase, eachhaving itssuction stroke at the same time as'the other and its-pressurestroke at the same: time as the other; Thus any surging which occurs inthe titrating chamber due to the pumping action is self compensating andthe tendency which otherwise would. exist for thesensing element tohunt: due to change in the concentration of. the: titration mixture oneach. pump cycle. is eliminated- The pumps will preferably deliver 10 tostrokes per minute and the chamber will preferably retain the:effluents: of 1.v to 2 minutes pumping. As later explained, a moreelaborate form of duplex pump adjustment will preferably be employed,but. it will be understood that the form of Figure 4 is adequate formany types of service and is useful to explainthe invention. Thesettings of the crank arms 54 and 55 will be adjusted to give thecorrect proportionality between the fractional sample and the samplereactant.

As seen in Figure 12 where extreme-accuracy in pumping of the sample andsample reagent into the titration chamber are required, each duplex pumpmay if preferred consist of a pair of constant feed pumps, 3| and 31 and35 and 35 preferably of the step valve type, and each having a commoninlet 30 or 36 and a common outlet 30 or 36 The pump pistons 50 and 50and and 5| in each pair are substantially 180 out of phase with respectto one another, so that each pair of pumps 3| and 3| and 35 and 35develops a constant delivery. The respective cranks 54' and 54 aresubstantially 180 out of phase with one another, and the same conditionprevails with the cranks 55 and 55 The connecting rods 56' and 56 and 51and 5'! are respectively adjustable. The actual structure shown inFigure 12 is merely suggestive of the more precise constant feed pumpswhich may be used on both sides of the duplex drive. See Sheen, Sheenand Sallfrank application Serial No. 778,316, filed October 7, 1947, forConstant Delivery Pump. With the form suggested in Figure, 12, a veryhigh degree of uniformity of pumping can be obtained both for the sampleand sample reagent entering the titration chamber. The following aretypical illustrations of the service to which the invention may beapplied.

Example I In the blanching of vegetables such as peas preparatory tocanning, the peas are subjected to a cold 0.2 normal solution of alkalisuch as sodium or potassium hydroxide. The concentration must be heldwithin plus or minus 0.02 normal. The peas are held in a conventionalreel type pea blancher which corresponds to container 20.

Alkalinity is constantly lost by drag out and by neutralization orcarbonation due to the peas. This concentration corresponds to a pHabove 11, which is very difficult to control by ordinary methods withinany such tolerance. As applied to the system of Figure 1, sodiumhydroxide solution forms the main reactant, and a bufiered acidsolution, suitably phosphoric acid, forms the sample reactant, thetitrating mixture being maintained at a range such as i9 or km on curve48 of Figure '3. It is thus possible to maintain a tolerance within plusor minus 0.004 normal, which is far better than that required for thisservice. Regulation may be at the range between trisodium phosphate anddisodium phosphate at pH 8 to 9, or at the range between disodiumphosphate and monosodium phosphate atpI-I 4 to 5 in the titratingchamber. While these are broad pH ranges, contral may be maintainedwithin plus or minus 0.2 pH.

Example II In this case the alkalinity concentration in container 20 iscontrolled for the purpose of textile bleaching, at a concentrationbetween 3.0 and 3.3% caustic soda in water. The main reactant 24 iscaustic soda solution while the sample reactant 34 is a buffer acid suchas phosphoric acid solution.

Example III A sulphuric acid bath 20 is to be held at 1% concentrationplus or minus 0.25%. In this case the main reactant is sulphuric acid,and the sample reactant is a buffer alkali, such as sodium borate.

Example IV The conductivity of an electroplating bath 20 is to bemaintained by addition of a salt, sodium ment to be turned on sulphate.In this case the main reactant is. sodium sulphate solution and thesample reactant is a diluent, distilled water.

Example V A strong bleaching solution containing chlorine or alkalimetal hypochlorite is to be held at a specified concentration. In thiscase the main reactant will be a water solution of. chlorine, a flow ofchlorine into water solution or a water solution of sodium hypochlorite,and the sample reactant will be sodium thiosulphate.

Example VI Example VII A strong peroxygen compound concentration such ascalcium peroxide is controlled by drawing off a fractional sample andintroducing it into the titration chamber, feeding into the titrationchamber a proportional amount of potassium permanganate solution as asample reactant, and also feeding in a dilute solution of sulphuric acidin proportional quantity. A triplex pump may be used with the extracylinder applied to the sulphuric acid, or it may be separately fed.

Example VIII A reducing wash 20 for textile dyeing is to be maintainedat a specified concentration ofsodium thiosulphate. In this case themain reactant is sodium thiosulphate and the sample reactant ispotassium dichromate solution.

It will be understood of course that the sens ing element will be of acharacter corresponding to the concentration which is being controlled,suitably a hydrogen ion electrode where pH is being controlled, aconductivity cell where conductivity is being controlled and anoxidation potential or other oxidation sensing element where oxidationpotential is being controlled.

The metering pumps employed at 3|, 35' and 46 will preferably be of thestep valve type as shown in Milton Roy Sheen U. S. Patents 2,263,- 429and 2,367,893.

i The preferred form of delivery adjustment for the pump is that shownin Milton Roy Sheen U. S. patent application Serial No. 654,180, filedMarch 13, 1946, for Stroke Control Mechanism, now to be described. Thismechanism is illustrated in Figures 5 to 10 hereof. Any other suitabletype of control of delivery as by automatic variable speed control canof course be used.

For pump 35' a similar microadjustment to that of Figures 5 to 10 may beused with hand adjustment to' permit adjustment during operation.

The controller 42 of Well known ty e causes the electric drive motor p58 for the stroke adjustand oil and reversed. A sultable type of motorwinding is shown having opposed coils 60 and 6| connected by end leads62 and 63 to the source through the control mechanism, with a centerlead 64 having a series accuse capacitor '65 and with-a-discriminatingswitch at on the control mechanism which determines when the motorwill'start or stop and which section of thewinding is to be actuated andtherefore in which direction the motor is to run on starting. It will beunderstood that this feature is intended to be diagrammaticallydisclosed merely. The drive from the stroke .control adjustment motor isthrough any suitable speed reduction 6"! to a sprocket 68 which is onanadjustment shaft 12 having the same axis as the adjustment head laterto be described. The sprocket It connects with a sprocket I5 on a wormshaft I6 by a chain H. The adjustment shaft I is in line with aiixcd-piv c'it E5, on the frame I6 supportedon base Ttandabout whichadjustment head '18 swings. The adjustment head-is driven in itsswinging path by an electric motor 85 having a speed reducing unit iiiand a crank 82 which may be c onnecte'd'to the opposite duplex pump unit(which with its adjustment head and related mechanism, if used, is notshown, as it is merely an opposite counterpart of that described). Theelectric motor 86 also drives a crank83 (in phase with crank8-2) whichmakes pivotal connection at 8 1 to a drivingli'nk 85 which ispivotally'connected to the adjustment head'IS at 85.

Under the action or this drive, theadjiistrhent head swings back andforth desirably'in an inva'riablepathat a frequency which is determinedby the speed adjustment on the motor. The linear relation of theadjustment and the change of stroke, and the condition of equality,later described, can very convenie'miyte obtained by regulating the arethrough which the adjustment head swings to 60 with as much precision asis necessary, and the arc of swing should then be equal on either sideof a line through the fixed pivot 75' of the adjustment headperpendicular to theaxis of the pum cylinder as later described.

The pump itself may be of any suitable type having a metering actionsuitably due to a reciprocating. piston and the following is intended toindicate a very desirable form.

The pump essentially comprises a cylinder 8'! having a reciprocatingpump piston 88 passing through packing 90 provided with a lubricationopening 9|. In this particular form of pump there are desirably usedmultiple inlet check valves 92 and 93 in series with one another, andmultiple outlet check valves .94 and 95 likewise in-series with oneanother. .Inletis providedat 96 and outlet at 97. The pumppistonisdesirably supported, moved'andguided by a crossheadBB' in crossheadguides I 00', lubricated at I I) I, the crosshead being either a part ofor an adjunct to the piston as preferred.

The piston is driven by the adjustment head through the interconnectingof a link I02 having pivoted connection to the crosshead at I03 andconnectin with the adjustment head at an adjustment pivot I04. Theadjustment pivot I04 moves along an adjustment path toward and away fromthe fixed pivot of the adjustment head in order to control the stroke.This movement is preferably accomplished by an adjustment screw I05having bearing support at I06 in the adjustment head and threading intoa nut I01 which supports the adjustment pivot and is guided slidably inways I08.

It is very convenient in obtaining the equalized 60 swing of theadjustment head to make the arm of the'driving crank 83 equal to theperpen 10 dicular distance of the pivot point of the-driving link on theadjustment head to the axis of the adjustmentscrew. v g V As theadjustment head'swings, the worm shaft swings back and forth with it butthe sprocket 12 on this shaft maintains its connection with the sprocket68 onthe fixed pivot axis by means of the chain M. I A

The interconnecting between the worm shaft and the adjustment screwmaybe accomplished by any suitable gearing, hereshown as a- Worm lid onthe worm shaft and a worm wheel III on the adjustment screw. Itisimportant to be-able to ascertain at any time the position of theadjustment pivot'pcint. With this object in view an indicator I I2 isprovided-at the top of the adjustment head, having a cover glass I I3showing a fast moving hand He and a slow moving hand II5 interconnectedwith theadjustment screw by suitable gearing II Ei forming no part ofthe present invention and described in'the aforesaidpapplication ofMilton Roy Sheen.

In operation, the pumping stroke will be relatively great with theadjustment pivot relatively far from the fixed pivot. With theadjustment pivot movedrelatively closer to the fixed pivotfithe strokeis shortened by an-amount preferably equal to the distance between therespectiveadjustment pivot positions.

g It will be evident thatany 'othersuitablestroke adjustment may beemployed in the present invention. I

The metering control canbe accomplished other ways, as indicated forexampletin Figure 1:1. In this form float orifice flow metercontrollers, for example of the Rotometer type, .are employedonthelfrac-tionalisampleeon the sample reagent and on the main reagent.:Float orifice fiow meter controllers of this character are'iihthemselves well known, and the detail .ther 'eof forms no part of thepresent invention.

As shown in Figure 11, the fractionalsample'is pumped by a pump II'I,preferably of the centrifugal type, driven by a motor H8; The' eiiluentfrom the pump I II passes through a controlvalve I20 and from the valvethrough the orifice an'd tapering verticalfioat chamberI2Iqof'afioat'orifice flow meter having a float I 22. Fromthe floatchamber the fractionalsamplepassestothe titration chamber '33. The float122 isinterconnected to a magnetic armature I'23'whi'ch is in inductiverelation to' a controlling zreactance I24 of a controller of any wellknown'type, suitably aself balancing reactance bridge orbalanc'ing relaysystem- I24. The: control valve I26 .isshow-n asmanipulated-bya'motor I2 drather'than' aihy draulicor pneumaticoperato'rassornetiin'es: used, wh1ch is controlled by the controller I24 throughWiring I26. The motor I25 restores balance on an opposite reactance I2'! connected to the controller by wiring I28. The device in eifectmaintains the valve I20 set at a constant fiow level as well known.

The sample reagent is pumped suitably by a centrifugal pump I30 drivenby a motor I3I through a valve I32. The same character of float orificeflow meter controller is used in this case and will not be separatelydescribed.

The main reagent is controlled by a similar system except that itresponds to the action of the v The eflluent passes through a valve I3!manipulated by a motor I38 which is controlled through wiring I 40 fromthe flow meter controller I 34.

The flow meter controller in this case employs its armature I23 inreactance I24 for indicating on the controller I34. It will be evidentthat other types of metering devices may be employed instead of thatshown in Figure 11.

It will be evident that the control of the main reagent shown in Figure11 or any other control of the flow of main reagent can be used with theduplex pump titration arrangement of Figure 1.

It will be evident that the centrifugal pumps 'II'I, I38 and I35 may ormay not be required individually or collectively depending upon thedifferential pressures available in the particular system.

In Figures 13 and 14 a typical titration chamber 33 is illustratedshowing sensing element 38 in the form of sensing electrodes 38', 38 anda temperature compensator 38 and the fractional sample pipe 30 and thesample reagent pipe 38.

Electrically driven stirring means is shown at It will be evident thatthe present invention provides a very simple, economical and convenientway of controlling concentration, particu- -larly in strong solutions.

In view of my invention and disclosure variations and modifications tomeet individual whim or particular need will doubtless become evident toothers skilled in the art, to obtain all or part .of the benefits of myinvention without copying .the structure shown, and I, therefore claimall such insofar as they fall within the reasonable spirit and scope ofmy claims.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. In a titration system, a first positive displacement pumphaving aplurality of inlet valves and a plurality of outlet valves in series,

' a second positive displacement pump having a "plurality of inletvalves and a plurality of outlet valves in series, a common driveconnected to the ,first and second pumps, which maintains the outermostinlet valve to the second pump, a pipe from the outermost outlet valveof the first pump and a pipe from the outermost outlet valve of thesecond pump connected together to combine the outputs of the partialsample and the sample reagent, a concentration sensing element incontact with the combined outputs, a container for a main reagent, apump for the main reagent, a pipe from the container for the mainreagent to the inlet of the pump for the main reagent, a pipe from theoutlet of the pump for the main reagent to the main body of liquid andautomatic controller means controlling the pump for the main reagent inresponse to the indication of the concentration sensing element.

2. In a titration system, a first positive displacement pump having aplurality of inlet valves and a plurality of outlet valves in series, asecond positive displacement pump having a plurality of inlet valves anda plurality of outlet valves in series, a common drive connected to thefirst and second pumps and synchronized with the suction and pressurestrokes in correspondence on the two pumps, a container for a main bodyof liquid whose concentration is to be controlled, a pipe from thecontainer for the main body to the outermost inlet valve of the firstpump, the delivery rate of the first pump being such as to divert thepartial sample from the main body, a container for a sample reagent, apipe from the container for the sample reagent to the outermost inletvalve to the second pump, a pipe from the outermost outlet valve of thefirst pump and a pipe from the outermost outlet valve of the second pumpconnected together to combine all outputs of the partial sample and thesample reagent, a concentration sensing element in contact with thecombined outputs, a container for a main reagent, a pump for the mainreagent, a pipe from the container for the reagent to the inlet of thepump for the main reagent, a pipe from the outlet of the pump for themain reagent to the main body of liquid and automatic controller meanscontrolling the pump for the main reagent in response to the indicationof the concentration sensing element.

ROBERT T. SHEEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 978,644 Raabe Dec. 13, 19101,375,200 Barnickel Apr. 19, 1921 1,684,645 Smith Sept. 18, 19281,857,922 Lewis May 10, 1932 2,345,465 Miles Mar. 28, 1944

1. IN A TITRATION SYSTEM, A FIRST POSITIVE DISPLACEMENT PUMP HAVING APLURALITY OF INLET VALVES AND A PLURALITY OF OUTLET VALVES IN SERIES, ASECOND POSITIVE DISPLACEMENT PUMP HAVING A PLURALITY OF INLET VALVES ANDA PLURALITY OF OUTLET VALVES IN SERIES, A COMMON DRIVE CONNECTED TO THEFIRST AND SECOND PUMPS, WHICH MAINTAINS THE PUMP DISCHARGESPROPORTIONAL, A CONTAINER FOR A MAIN BODY OF LIQUID WHOSE CONCENTRATIONIS TO BE CONTROLLED, A PIPE FROM THE CONTAINER FOR THE MAIN BODY TO THEOUTERMOST INLET VALVE OF THE FIRST PUMP, THE DELIVERY RATE OF THE FIRSTPUMP BEING SUCH AS TO DIVERT A PARTIAL SAMPLE FROM THE MAIN BODY, ACONTAINER FOR A SAMPLE FROM THE MAIN FROM THE CONTAINER FOR THE SAMPLEREAGENT, TO THE OUTERMOST INLET VALVE TO THE SECOND PUMP, A PIPE FROMTHE OUTERMOST OUTLET VALVE OF THE FIRST PUMP AND A PIPE FROM THEOUTERMOST OUTLET VALVE OF THE SECOND PUMP CONNECTED TOGETHER TO COMBINETHE OUTPUTS OF THE PARTIAL SAMPLE AND THE SAMPLE REAGENT, ACONCENTRATION SENSING ELEMENT IN CONTACT WITH THE COMBINED OUTPUTS, ACONTAINER FOR A MAIN REAGENT, A PUMP FOR THE MAIN REAGENT, A PIPE FROMTHE CONTAINER FOR THE MAIN REAGENT TO THE INLET OF THE PUMP FOR THE MAINREAGENT PIPE FROM THE OUTLET OF THE PUMP FOP THE MAIN REAGENT TO THEMAIN BODY OF LIQUID AND AUTOMATIC CONTROLLER MEANS CONTROLLING THE PUMPFOR THE MAIN REAGENT IN RESPONSE TO THE INDICATION OF THE CONCENTRATIONSENSING ELEMENT.